Process of treating aluminum with halogen gases



' Patented Jan. 14, 1930 UNITED STATES PATENT- 'orrice ROBERT J.ANDERSON, OF IAIRMON T, WEST VIRGINIA, ASSIGNOR TO FAIRMONT MANU-FACTURING COMPANY, OF FAIRMONT, WEST VIRGINIA, A CORPORATION OF WEST 1etc.

VIRGINIA PROCESS OF TREATING ALUMINUM WITH HALOGEN GASES No Drawing.Application filed May 1;

My invention relates to a process of treatin molten metals, includingalloys, with ha ogen gases, and has relation especially to the treatmentof aluminum and its alloys to improve their mechanical characteristics.

Molten metals, by which I mean to include alloys, and particularlyaluminum and its alloys, may, and usually do, contain dissolved gasesand other impurities, such as foreign suspended matter. The dissolvedgases present in a metal depend upon the. particular metal, theconditions under which the same is melted, the process of manufacture,etc., and, generally speaking, the gases present cannot be controlledeffectively, or at all, under the conditions of manufacture. Wheredissolved gases are present in metals the effect is to cause porosity inthe castings made therefrom, which is, of course, of great moment infoundry practice as it leads to rejection of castings, weakness,breakages,

It is found that metals dissolve increasing quantities of gases withincreasing temperature of melting, thus departing from Henrys law whichapplies to other liquids. Also, such metal-gas solutions tend to remainsaturated. That is to say, as the temperature is decreased from a highertem erature the molten metal does not give 0 gas at the same rate atwhich the gas was taken up, and, on solidifying, there is a tendency fora considerable volume of gas to be evolved, causing blow-holes andporosity.

I have discovered that these gases, and also other deleterious suspendedsolid .impurities, by which term I mean to include solids which becomemolten or not whenthe body of metal is melted, may be removed bytreatment of the metal with a halogen gas, such, for example, aschlorine, bromine, or fluorine, and that this is particularly true whenusing such a gas which is only dissolved with difiiculty by the metal ata given temperature. It is also desirable to use in this connection, agas which does 'not combine to an undesirable extent with the metalitself. However, gases which do combine with the metals may be, and areused in my process with effective results.

The object of my invention'is, therefore,

1928. Serial No. 274,360.

to remove such gases and other deleterious matters from metals in theabove manner. The theory of the action of the removal thereof is notentirely known but it is believed that the action comprises mainly theremoval of the dissolved gases and other deleterious impuritiesmechanically by agitation due to the introduction'of the gas or gaseousmaterials as above referred to, although there may be, also, somecombination brought about with the dissolved gases, or other deleteriousimpuriti'es, as well. The deleterious solid impurities which are removedin this way are of various kinds, ac

cording to the particular kind of metal treated. These comprise thevarious suspended solid impurities present in the different metals, suchasdirt, oxides, nitrides, carbides,etc. In the case of aluminum, forexample, and its alloys, I have demonstrated that clean aluminum made bybeing subjected to my process, has very superior mechanical propertiesas compared with aluminum which has not been subjected to my process. Infact, in all such metals, not only do solid non-metallic impuritiesproduce zones of weakness around the inclusions as referred to, but suchimpurities when present even in relatively small ercentages, have beenfound to have a profound influence on the mechanical properties, as wellas on the working, rollingandcasting qualities of the different metals.Also, the metal so treated is found to have greatly increased strengthand to be capable of much greater elongation. In fact, it has been foundpreviousl Y substantially impossible. to remove or re uce by anypreviously known method small percentages of impuritiessueh, as can beremoved by myprocess. I have found that even very small percentages ofimpurities may be practically entirely removed by treatment in myprocess.

lVhile my invention is capable of embodiment in many different forms,for the purpose of illustration I shall describe only certain formsof myinvention hereinafter.

' For example, in carrying outmy invention I may use any desired-halogengas,

such, for instance, as chlorine, bromine or f fluorine. For instance, intreating aluminum I provide a bath of molten aluminum which may have anydesired temperature, such as 700 (1, or above, and then apply chlorinegas to the metalas by bubbling it through the molten metal until theimpurities I are substantially entirel removed. Thiswill ordinarilycomprise t e introduction of nascent chlorine into the metal so that,say 1 cu. ft.-of chlorine, referred to standard conditions oftemperature and pressure. is introduced per 300 lbs. of aluminum,-afterwhich the metal may be poured to form a finished or semi-finishedcasting. In this treatment the chlorine gas may be applied to the metalin any desired way and in any desired type of apparatus, but, for

7 ing a SOlld impurity while remainin example, the gas may be lnjectcdinto the metal with the aid of a perforated pipe which may be located inthe metal in such a Way that the perforations therein for the dischargeof the chlorine are located at the bottom of the molten aluminum. The

chlorine combines with the aluminum nitride or carbide, and the.dissolved gases, etc., driven out pass out into the atmosphere. Thechlorine bubbling upwardly through the liquid has an agitating actionwhich removes the foreign suspended materials due to the resultantupward currents 6. The process which comprises removing an impurity fromaluminum by the application of chlorine thereto.

7. The process which comprises removing a gaseous impurity from aluminumcarrying the same by the application of chlorine thereto.

8. The process which comprises removing a solid impurity while' remaininin solid form from aluminum bythe-application of therein] Thoseimpurities which do not combine chemically with the chlorine rise to thesurface, forming a scum or dross,

which is removed by skimming. In the case of aluminum, the impuritiesresent may be reduced in this way to practically nil.

While I have described my invention above in detail I wish it to beunderstood that many changes may be made therein without departing fromthe spirit of. the same.

I claim:

1...The process which comprises removing an impurity from aluminumcontaining aluminum oxide as an impurity by the application of halogengas thereto so as to combine with the aluminum oxide therein.

2. The process which comprises removing an impurity from aluminumcontaining.

aluminum oxide carbide and nitride as impurities by the application of ahalogen gas.

thereto so as to combine with the aluminum oxide, also with aluminumcarbide and a gaseous impurity from aluminum, carrying.

the same by the application of a halogen gas thereto.

5. The process which comprises removsolid form from aluminum by the. appication of a'halogen gas thereto.

